The prop gun fired by Alec Baldwin on-set that accidentally killed a cinematographer and injured a director on Thursday (October 21) contained "a live round," the International Alliance of Theatrical Stage Employees confirmed to IndieWire.

IATSE Local 44, which covers prop masters, confirmed the weapon contained "a live round" and that the propmaster was not a member of Local 44 in an email sent on Friday (October 22).

On Thursday, NBC News reported director of photography, Halyna Hutchins, 42, was killed during the accidental shooting, while director, Joel Souza, 48, was injured, the Santa Fe County Sheriff's Office confirmed in a statement.

The union confirmed in the email to IndieWire that Souza was released from a local hospital after receiving treatment.

Baldwin addressed the accident in a statement obtained by TMZ Friday morning.

"There are no words to convey my shock and sadness regarding the tragic accident that took the life of Halyna Hutchins, a wife, mother and deeply admired colleague of ours," Baldwin said "I'm fully cooperating with the police investigation to address how this tragedy occurred. I am in touch with with her husband, offering my support to him and his family. My heart is broken for her husband, their son, and all who knew and loved Halyna."

An eyewitness on the set of the Santa Fe film Rust told Showbiz 411 they heard a distraught Baldwin repeatedly say, “In all my years, I’ve never been handed a hot gun," meaning a gun with real ammunition.

Hutchins was airlifted to the University of New Mexico Hospital in Albuquerque, where she was pronounced dead.

The witness told Showbiz 411 that Baldwin, 63, was immediately taken to a hospital after the shooting and "had no idea how badly they were hurt or Halyna was dead."

The Santa Fe New Mexican reported Baldwin was seen Thursday while speaking on the phone outside the Santa Fe County Sheriff's Office.

"There was an accident today on the New Mexico set of 'Rust involving the misfire of a prop gun with blanks," a spokesperson for Baldwin said in a statement obtained by NBC News on Thursday. "Production has been halted for the time being. The safety of our cast and crew remains our top priority."

No charges have been filed in relation to the shooting, but authorities confirmed it remains under an active investigation.

“We’re treating this as we would any other investigation,” Sheriff's Office spokesman Juan Rios said via NBC News, adding that deputies were still determining whether the shooting was accidental.

Baldwin is one of the film's stars and also serves as a producer.